As may be deduced from the above-identified copending application and the U.S. patents mentioned above, as well as from the references specifically made of record below, mixing heads have been utilized heretofore for the intensive mixing of two or more reactive components which, like a polyol and di-isocyanate or polyisocyanate, are capable of reaction to form a settable synthetic resin composition such as a polyurethane. Such mixing heads may open into a space in which the reacting components are to be received in the form of the reacting mixture, e.g. a mold.
Such heads can be provided with inlets, nozzles or orifices through which the respective components can be fed to the mixing chamber of the head, the mixing chamber having an outlet turned toward the mold or other cavity adapted to receive the reacting mixture.
Thus, for example, German Pat. No. 20 97 935 discloses a device or mixing head for the mixing of two or more interreactive synthetic resin components, each of which is introduced through a respective inlet nozzle into the mixing chamber, the jets being trained upon one another to promote the intimate mixing. The mixture emerges from an outlet of the mixing chamber and the latter is so formed that a longitudinally shiftable control piston or plunger can be displaced from one end position in which the nozzles are unblocked and mixing as well as discharge of the mixture are permitted, into another end position in which the nozzles are blocked and the mixture within the chamber is expelled by the plunger into the mold.
To prevent fluid components in the various passages from stagnating, the control plunger can be provided with bypass passages which can bypass the flow of the respective component from the nozzle to return passages in a recirculating system provided with a pump or the like.
To control the backpressure within the mixing chamber as seen by the incoming stream of each component, it has been proposed to introduce into the mixing chamber a body which partially obstructs, constructs or occupies a portion of the flow cross-section or volume. (See the aforementioned copending application and German Pat. No. 20 65 841 and German printed application No. 26 12 812).
It is also known, in this connection, to conduct the mixture into a calming or quiescence chamber prior to its passage into the mold, the calming chamber or quiescence chamber lying at a right angle to the mixing chamber as described in German Pat. No. 23 27 269 or German open application No. 29 07 938, for example.
While all of the various improvements on the basic system have been effective to various degress in assuring effective mixing of two or more components for the purposes described, the problem has not been solved completely heretofore, especially for components which are less radially miscible with one another and which do not, as readily, form miscible mixtures. There is a desire to use such less miscible components, however, because they generally are less expensive than the more readily miscible substances.